Enzyme immunoassays are rapidly replacing comparable assay systems which currently employ radioisotopes as a means of detection. These systems have the advantages of a choice of substrates for different applications, as well as, minimizing the instrumentation necessary for quantitative determinations. EIA's are currently being applied in the fields of genetic engineering for product detection, microbiology for antigen detection and antibody titration, and in the field of clinical chemistry for the detection of minute levels of biological compounds such as hormones. Pilot work into alternative methods of detection can evaluate the feasibility of these alternatives and if successful extend the usefulness and applicability of the rapidly growing numbers of enzyme immunoassay systems currently being developed. This proposal deals with two high risk variations applicable to many of the existing enzyme immunoassay techniques. One variation is to identify the presence of several hormones or other antigens in a single sample containing from one to all of these analytes. The other variation concerns evaluating endpoints which take advantage of the extreme sensitivity and range of resistance and conductance measuring devices. We have proposed to apply these innovations to the Competitive Enzyme Linked Immunoassay (CELIA) system which we have invented and used for the past 5 years. CELIA is a well established protocol which will permit reliable evaluation of the modifications which we are proposing. Both of the proposed variations require extensive testing on a variety of antigens to demonstrate their feasibility. Because of the uncertain nature of this research, pilot work is necessary to screen the many potential reactions possible for the electronic endpoint determination. Similarly, the kinetics of the multiple assay approach require that preliminary studies be made to determine understanding the full potential of simultaneously assaying for 10 to 100 different antigens in a single test sequence.